Embedded printed circuit board and method of manufacturing the same

ABSTRACT

Disclosed is an embedded printed circuit board, in which electronic devices having different thicknesses can be embedded together, thus achieving highly dense electronic devices, and when electronic devices having considerably different thicknesses are embedded, two electronic devices which are comparatively thinner can be embedded in a perpendicular direction, thus reducing an embedding area and suppressing warping of the printed circuit board, and an insulating member the thickness of which is variably adjusted is interposed between base substrates, so that spaces between the electronic devices are completely filled therewith, thus solving the problem of void defects, resulting in reliable printed circuit boards, and, when a base substrate includes a core made of metal, the printed circuit board can less warp. Also a method of manufacturing the embedded printed circuit board is provided.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.10-2010-0093742, filed Sep. 28, 2010, entitled “Embedded substrate and amethod for manufacturing the same”, which is hereby incorporated byreference in its entirety into this application.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to an embedded printed circuit board and amethod of manufacturing the same.

2. Description of the Related Art

Alongside the advances being made in the electronics industry, thedemand to reduce the size of electronic components is increasing. Thereis a recent market trend to fabricate electronic products which arelight, slim, short and small this trend continues to achieve printedcircuit boards (PCBs) that are slim. Accordingly, different types ofmounting methods for devices from conventional surface mount techniquesare beginning to make their appearance, and attention is being given tothe development of PCBs with embedded electronic devices, that is, PCBshaving active devices such as an IC (Integrated Circuit) or passivedevices such as capacitors mounted inside of them, in order to ensurehighly dense components and high reliability.

Conventional methods of embedding electronic devices include embeddingan electronic device using a base substrate having a thicknesscorresponding to a thickness of the embedding electronic device, and, asnecessary, building-up base substrates having electronic devicesembedded therein, thus forming a multilayered PCB. However, suchconventional methods are problematic because the range of the basesubstrate that can be selected is limited because of a restriction inwhich the thickness of the base substrate of the PCB should correspondto the thickness of the electronic device. Furthermore, in the casewhere a plurality of electronic devices is embedded in a single-layerbase substrate, the plurality of electronic devices which will beembedded should be selected only from among those having the samethickness or a similar thickness. If two or more electronic deviceshaving different thicknesses are embedded in a single-layer basesubstrate, a base substrate having a thickness corresponding to thethickest electronic device among them should be used. As such, in orderto completely embed a comparatively thin electronic device, theinsulating material must be as thick as a difference in thicknessbetween the electronic devices, undesirably causing the problem of voiddefects in the insulating material and making it difficult to attainreliable PCBs.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind theproblems encountered in the related art and the present invention isintended to provide an embedded PCB, in which a plurality of electronicdevices having different thicknesses is able to be embedded in asingle-layer base substrate, and also to provide a method ofmanufacturing the same.

An aspect of the present invention provides an embedded PCB, comprisinga first base substrate having a first device embedded therein, a secondbase substrate having a second device embedded therein, an insulatingmember formed between one surface of the first base substrate and onesurface of the second base substrate, a third device which is embeddedto pass through the first base substrate, the second base substrate andthe insulating member and is thicker than the first device and thesecond device, a first copper clad laminate formed on the other surfaceof the first base substrate and including a first insulating layer and afirst outer circuit layer formed on an outer surface of the firstinsulating layer, and a second copper clad laminate formed on the othersurface of the second base substrate and including a second insulatinglayer and a second outer circuit layer formed on an outer surface of thesecond insulating layer.

In this aspect, the embedded PCB may further comprise a first via forelectrically connecting the first outer circuit layer with the firstdevice, a second via for electrically connecting the second outercircuit layer with the second device, and a third via for electricallyconnecting the second outer circuit layer with the third device.

In this aspect, the first base substrate and the second base substratemay be formed of a metal layer.

In this aspect, the first base substrate may comprise a first core layerand a first inner circuit layer formed on an outer surface of the firstcore layer, and the second base substrate may comprise a second corelayer and a second inner circuit layer formed on an outer surface of thesecond core layer.

In this aspect, the first device and the second device may be formed ina line in a direction perpendicular to the insulating member.

Another aspect of the present invention provides a method ofmanufacturing an embedded PCB, comprising (A) forming a first cavity anda third cavity in a first base substrate, disposing a first device inthe first cavity, disposing a third device in the third cavity, andfixing the first device and the third device, (B) forming a secondcavity and a fourth cavity that corresponds to the third cavity in asecond base substrate, disposing a second device in the second cavity,and fixing the second device, (C) providing an insulating member havinga through hole at a position corresponding to the third cavity and thefourth cavity, (D) disposing the first base substrate and the secondbase substrate so that one surface of the first base substrate and onesurface of the second base substrate face each other, interposing aninsulating member between one surface of the first base substrate andone surface of the second base substrate, and pressure laminating thefirst base substrate, the second base substrate and the insulatingmember together and (E) forming a first copper clad laminate on theother surface of the first base substrate, and forming a second copperclad laminate on the other surface of the second base substrate.

In this aspect, (A) may comprise (A′) forming a first cavity and a thirdcavity in a first base substrate, attaching a first adhesive layer tothe other surface of the first base substrate, disposing a first devicein the first cavity, and disposing a third device in the third cavity,and fixing the first device and the third device, and (B) may comprise(B′) forming a second cavity and a fourth cavity that corresponds to thethird cavity in a second base substrate, attaching a second adhesivelayer to the other surface of the second base substrate, disposing asecond device in the second cavity and fixing the second device, and themethod may further comprise (D′) removing the first adhesive layer andthe second adhesive layer, between (D) and (E).

In this aspect, (D) may further comprise (D′) disposing the first basesubstrate, the second base substrate and the insulating member so thatthe third device formed in the first base substrate is disposed in thefourth cavity of the second base substrate through the through hole ofthe insulating member.

In this aspect, (E) may comprise providing a first copper clad laminatecomprising a first insulating layer and a first outer circuit layerformed on an outer surface of the first insulating layer, layering thefirst copper clad laminate on the other surface of the first basesubstrate, providing a second copper clad laminate comprising a secondinsulating layer and a second outer circuit layer formed on an outersurface of the second insulating layer, and layering the second copperclad laminate on the other surface of the second base substrate.

In this aspect, the method may further comprise, after (E), (G) forminga first via for electrically connecting the first outer circuit layerwith the first device, a second via for electrically connecting thesecond outer circuit layer with the second device, and a third via forelectrically connecting the second outer circuit layer with the thirddevice.

In this aspect, the first base substrate in (A) and the second basesubstrate in (B) may be formed of a metal layer.

In this aspect, the first base substrate in (A) may comprise a firstcore layer and a first inner circuit layer formed on an outer surface ofthe first core layer, and the second base substrate in (B) may comprisea second core layer and a second inner circuit layer formed on an outersurface of the second core layer.

In this aspect, the first device and the second device in (D) may beformed in a line in a direction perpendicular to the insulating member.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention will be moreclearly understood from the following detailed description taken inconjunction with the accompanying drawings, in which:

FIGS. 1 and 2 are cross-sectional views showing embedded PCBs accordingto embodiments of the present invention; and

FIGS. 3 to 9 are cross-sectional views showing a process ofmanufacturing the embedded PCB according to the embodiment of thepresent invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail while referring to the accompanying drawings. Throughout thedrawings, the same reference numerals are used to refer to the same orsimilar elements. Moreover, descriptions of known techniques, even ifthey are pertinent to the present invention, are regarded as unnecessaryand may be omitted when they would make the characteristics of theinvention and the description unclear.

Furthermore, the terms and words used in the present specification andclaims should not be interpreted as being limited to typical meanings ordictionary definitions, but should be interpreted as having meanings andconcepts relevant to the technical scope of the present invention basedon the rule according to which an inventor can appropriately define theconcept implied by the term to best describe the method he or she knowsfor carrying out the invention.

Embedded PCB

FIGS. 1 and 2 are cross-sectional views showing embedded PCBs accordingto embodiments of the present invention.

As shown in FIGS. 1 and 2, the embedded PCB according to the presentembodiment includes a first base substrate 10 having a first device 110embedded therein, a second base substrate 20 having a second device 120embedded therein, an insulating member 30 formed between one surface ofthe first base substrate 10 and one surface of the second base substrate20, a third device 130 which is embedded to pass through the first basesubstrate 10, the second base substrate 20 and the insulating member 30and is thicker than the first device 110 and the second device 120, afirst copper clad laminate 40 formed on the other surface of the firstbase substrate 10 and including a first insulating layer 40 b and afirst outer circuit layer 40 a formed on the outer surface of the firstinsulating layer 40 b, a second copper clad laminate 50 formed on theother surface of the second base substrate 20 and including a secondinsulating layer 50 b and a second outer circuit layer 50 a formed onthe outer surface of the second insulating layer 50 b, a first via 60which electrically connects the first outer circuit layer 40 a with thefirst device 110, a second via 70 that electrically connects the secondouter circuit layer 50 a and the second device 120, and a third via 80that electrically connects the second outer circuit layer 50 a and thethird device 130.

The first base substrate 10 includes a first core layer 10 b and a firstinner circuit layer 10 a, and the first inner circuit layer 10 a isformed on the outer surface of the first core layer 10 b. Specifically,the first inner circuit layer 10 a is electrically insulated from thefirst outer circuit layer 40 a by means of the first insulating layer 40b. Also, the second base substrate 20 includes a second core layer 20 band a second inner circuit layer 20 a, and the second inner circuitlayer 20 a is formed on the outer surface of the second core layer 20 b.As such, the first core layer 10 b and the second core layer 20 b may beformed of an insulating material.

On the other hand, the first base substrate 10 and the second basesubstrate 20 may be formed of a metal layer (FIG. 2). The first basesubstrate 10 and the second base substrate 20, which are formed of themetal layer, are advantageous because they are more rigid than the firstbase substrate 10 including the first core layer 10 b made of aninsulating material and the first inner circuit layer 10 a formed on theouter surface of the first core layer 10 b and the second base substrate20 including the second core layer 20 b made of an insulating materialand the second inner circuit layer 20 a formed on the outer surface ofthe second core layer 20 b, and thus the resulting embedded PCB hashigher resistance to external stress and can less warp.

The thickness of the insulating member 30, which is formed between onesurface of the first base substrate 10 and one surface of the secondbase substrate 20 and laminated together, may be variably adjustedduring the fabrication of the embedded PCB, and such an insulatingmember 30 is maintained in a semi-cured state before being subsequentlycured to manufacture a product. Hence, the insulating member 30 maysuffice as the required amount of resin between the base substrates, andalso may efficiently charge the empty space between the elements whileflowing in the PCB.

The first copper clad laminate 40 and the second copper clad laminate 50are respectively formed on the outer surfaces of the base substrates,which have the plurality of devices embedded therein and are pressurelaminated together. The first copper clad laminate 40 includes the firstinsulating layer 40 b and the first outer circuit layer 40 a formed onthe outer surface of the first insulating layer 40 b, and the secondcopper clad laminate 50 includes the second insulating layer 50 b andthe second outer circuit layer 50 a formed on the outer surface of thesecond insulating layer 50 b.

The embedded PCB according to the present invention is configured suchthat the first device 110, the second device 120 and the third device130 are disposed in the base substrates, in which the first device 110has the same thickness as that of the first base substrate 10 and thesecond device 120 has the same thickness as that of the second basesubstrate 20.

The third device 130 is thicker than the first device 110 and the seconddevice 120. Alternatively, a device which is thicker than the sum of thethicknesses of the first device 110 and the second device 120 may beadopted as the third device 130.

Furthermore, the first device 110 and the second device 120 may beformed in a line in a direction perpendicular to the insulating member30. In this case, the PCB may be symmetric, and thereby warping of theentire PCB may be suppressed, and the embedding density of electronicdevices may be increased.

The vias 60, 70, 80 function to electrically connect the first outercircuit layer 40 a or the second outer circuit layer 50 a with the firstdevice 110, the second device 120 or the third device 130.

Specifically, the first via 60 which functions to electrically connectthe first outer circuit layer 40 a with the first device 110 may beformed by disposing a pad of the first device 110 toward the first outercircuit layer 40 a, forming a via hole to correspond to the pad andfilling the via hole with a conductive metal such as Cu Likewise, thesecond via 70 functions to electrically connect the second outer circuitlayer 50 a with the second device 120, and the third via 80 functions toelectrically connect the first outer circuit layer 40 a or the secondouter circuit layer 50 a with the third device 130 depending on thedirection of a pad of the third device 130.

Method of Manufacturing Embedded PCB

FIGS. 3 to 9 are cross-sectional views showing a process ofmanufacturing the embedded PCB according to the embodiment of thepresent invention. With reference thereto, the method of manufacturingthe embedded PCB according to the present embodiment is described below.

As shown in FIG. 3, a first cavity 15 and a third cavity 17 are formedin a first base substrate 10, and a first adhesive layer 11 is attachedto the other surface of the first base substrate 10, after which a firstdevice 110 is disposed in the first cavity 15 and a third device 130 isdisposed in the third cavity 17, followed by fixing these devices to thefirst adhesive layer 11.

In order to manufacture the embedded PCB according to the presentembodiment, the first device 110 having the same thickness as that ofthe first base substrate 10 is embedded in the first base substrate 10.Specifically, as shown in FIG. 3, a first base substrate 10 having thesame thickness as that of the first device 110 is prepared. Thereafter,a portion of the first base substrate 10 as large as the size of thefirst device 110 is perforated so that the first device 110 can beembedded in the first base substrate 10, thus forming the first cavity15. Furthermore, a portion of the first base substrate 10 as large asthe size of the third device 130 is perforated so that the third device130 which is thicker than the first device 110 can pass through thefirst base substrate 10, thus forming the third cavity 17. Thereafter,the first adhesive layer 11 is attached to the other surface of thefirst base substrate 10. As such, the first adhesive layer 11 istemporarily used to fix the first device 110 and the third device 130 tothe first base substrate 10.

More specifically, the first device 110 is disposed in the first cavity15 in such a manner that a pad of the first device 110 is disposed inthe direction of being inserted into the first cavity 15 and theninserted (face down), and the first device 110 is then attached to thefirst adhesive layer 11. As such, the pad of the first device 110 isflush with the other surface of the first base substrate 10, and thelower surface of the first device 110 is flush with one surface of thefirst base substrate 10. Furthermore, the third device 130 is disposedin the third cavity 17 and then attached to the first adhesive layer 11.As such, because the third device 130 is thicker than the first basesubstrate 10, when the disposed third device 130 is attached to thefirst adhesive layer 11, the lower surface of the third device 130 isflush with the other surface of the first base substrate 10, and the padof the third device 130 may be provided in the form of protruding fromone surface of the first base substrate 10.

Next, as shown in FIG. 4, a second cavity 25 and a fourth cavity 27 thatcorresponds to the third cavity 17 are formed in a second base substrate20, a second adhesive layer 21 is attached to the other surface of thesecond base substrate 20, and then a second device 120 is disposed inthe second cavity 25 and fixed to the second adhesive layer 21. Thesecond base substrate 20 includes a second core layer 20 b and a secondinner circuit layer 20 a, the second inner circuit layer 20 a beingformed on the outer surface of the second core layer 20 b. As such, thesecond core layer 20 b may be made of an insulating material.Specifically, as seen in FIG. 4, a second base substrate 20 having thesame thickness as that of the second device 120 is prepared, and aportion of the second base substrate 20 as large as the size of thesecond device 120 is perforated so that the second device 120 can beembedded in the second base substrate 20, thus forming the second cavity25. Furthermore, a portion of the second base substrate 20 as large asthe size of the third device 130 is perforated so that the third device130 which is thicker than the first device 110 can pass through thesecond base substrate 20, thus forming the fourth cavity 27. Thereafter,the second adhesive layer 21 is attached to the other surface of thesecond base substrate 20. As such, the second adhesive layer 21 istemporarily used to fix the second device 120 to the second basesubstrate 20.

More specifically, the second device 120 is disposed in the secondcavity 25 in such a manner that a pad of the second device 120 isdisposed in the direction in which it is inserted into the second cavity25 and inserted (face up), and then the second device 120 is attached tothe second adhesive layer 21. In this case, the pad of the second device120 is flush with the other surface of the second base substrate 20, andthe lower surface of the second device 120 is flush with one surface ofthe second base substrate 20. The fourth cavity 27 is used to insert thethird device 130, which is fixed to and protrudes from the first basesubstrate 10, in a subsequent process.

Also, the first adhesive layer 11 and the second adhesive layer 21 areused to fix the first device 110, the second device 120, and the thirddevice 130, and do not have to have a layer structure having adhesiveforce. Furthermore, because these adhesive layers are removed afterbeing used and are not permanent, a typical adhesive such as an adhesivefilm may be used. Alternatively, the adhesive layers may be omitted asfar as the device may be fixed to the base substrate without even usingthe adhesive.

Next, as shown in FIG. 5, an insulating member 30 having a through hole35 at a position corresponding to the third cavity 17 and the fourthcavity 27 is prepared.

As such, the thickness of the insulating member 30 may be variable.Thus, in the case where the third device 130 is much thicker than thesum of thicknesses of the first device 110 and the second device 120,the thickness of the insulating member 30 may compensate for thedifference in thickness between the devices, thus solving the problem ofvoid defects in the PCB.

Taking into consideration the thickness of the first device 110, thesecond device 120 and the third device 130, the thickness of theinsulating member 30 is determined. For instance, the thickness of theinsulating member 30 may be set so that the first base substrate 10 andthe second base substrate 20 are pressure laminated and then the pad ofthe third device 130 can be fixed to the first adhesive layer 11 throughthe second base substrate 20.

The insulating member 30 is maintained in a semi-cured state beforebeing cured in a subsequent process, and thus exhibits superior chargingcapability and resin flowability, and may be efficiently charged betweenthe first device 110 and the first cavity 15, between the second device120 and the second cavity 25, or between the third device 130 and thethird cavity or the fourth cavity 27.

Next, as shown in FIG. 6, the first base substrate 10 and the secondbase substrate 20 are disposed so that one surface of the first basesubstrate 10 and one surface of the second base substrate 20 face eachother, and the insulating member 30 is interposed between one surface ofthe first base substrate 10 and one surface of the second base substrate20.

Specifically, the first base substrate 10, the second base substrate 20and the insulating member 30 are disposed such that the third deviceformed in the base substrate 10 is inserted into the fourth cavity ofthe second base substrate 20 through the through hole 35 of theinsulating member 30.

Next, as shown in FIG. 7, the first base substrate 10, the second basesubstrate 20, and the insulating member 30 are pressure laminatedtogether, and the first adhesive layer 11 and the second adhesive layer21 are removed. As shown in FIGS. 6 to 9, the first device 110 and thesecond device 120 may be formed in a line in a direction perpendicularto the insulating member 30.

Next, as shown in FIG. 8, a first copper clad laminate 40 is layered onthe other surface of the first base substrate 10, and a second copperclad laminate 50 is layered on the other surface of the second basesubstrate 20.

Specifically, the first copper clad laminate 40 including a firstinsulating layer 40 b and a first outer circuit layer 40 a formed on theouter surface of the first insulating layer 40 b is prepared, and thefirst insulating layer 40 b is disposed to come into contact with theother surface of the first base substrate 10. Furthermore, the secondcopper clad laminate 50 including a second insulating layer 50 b and asecond outer circuit layer 50 a formed on the outer surface of thesecond insulating layer 50 b is prepared, and the second insulatinglayer 50 b is disposed to come into contact with the other surface ofthe second base substrate 20.

Next, as shown in FIG. 9, a first via 60 is formed to electricallyconnect the first outer circuit layer 40 a with the first device 110, asecond via 70 is formed to electrically connect the second outer circuitlayer 50 a with the second device 120, and a third via 80 is formed toelectrically connect the second outer circuit layer 50 a with the thirddevice 130.

Specifically, a photosensitive resist (not shown) is applied on an outercircuit layer (including the first outer circuit layer and the secondouter circuit layer), and an opening that exposes a via forming portionis formed. As such, the opening may be formed by subjecting thephotosensitive resist other than the via forming portion tophoto-exposure, and then removing the unexposed photosensitive resistapplied on the via forming portion using a developer. An example of thephotosensitive resist may include a dry film or a liquid photoresist.Thereafter, the portion of the outer circuit layer exposed by theopening is removed from the outer circuit layer (including the firstouter circuit layer and the second outer circuit layer). Thereafter, thephotosensitive resist is removed using a stripper such as NaOH or KOH.Thereafter, the insulating layer (including the first insulating layerand the second insulating layer) of the via forming portion is processedthus forming a via hole. The via hole may be processed using a CNC(Computer Numerical Control) drill, CO₂ or Yag laser drill. Thereafter,the via hole is plated thus forming a via 60, 70, 80.

On the other hand, the first base substrate 10 and the second basesubstrate 20 may be formed of a metal layer. In the case where anembedded PCB is manufactured using base substrates made of a metallayer, the manufacturing process thereof may be the same as the onementioned above.

As described hereinbefore, the present invention provides an embeddedPCB and a method of manufacturing the same. According to the presentinvention, electronic devices having different thicknesses can beembedded together, thus achieving highly dense electronic devices.

As such, when the electronic devices having considerably differentthicknesses are embedded, two electronic devices which are comparativelythinner can be embedded in a perpendicular direction, thus reducing anembedding area and suppressing warping of the PCB.

Also, according to the present invention, an insulating member thethickness of which is variably adjusted is interposed between basesubstrates, so that spaces between the electronic devices are completelyfilled therewith, thus solving the problem of void defects in the PCB,resulting in reliable PCBs.

Also, according to the present invention, in the case where the basesubstrate includes a core made of metal, resistance to stress applied tothe PCB can become stronger, thus suppressing warping of the PCB.

Although the embodiments of the present invention regarding the embeddedPCB and the method of manufacturing the same have been disclosed forillustrative purposes, those skilled in the art will appreciate that avariety of different modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims. Accordingly, suchmodifications, additions and substitutions should also be understood asfalling within the scope of the present invention.

1. An embedded printed circuit board, comprising: a first base substratehaving a first device embedded therein; a second base substrate having asecond device embedded therein; an insulating member without a circuitpattern formed between one surface of the first base substrate and onesurface of the second base substrate; a third device which is embeddedto pass through the first base substrate, the second base substrate andthe insulating member and is thicker than the first device and thesecond device; a first copper clad laminate formed on the other surfaceof the first base substrate and including a first insulating layer and afirst outer circuit layer formed on an outer surface of the firstinsulating layer; and a second copper clad laminate formed on the othersurface of the second base substrate and including a second insulatinglayer and a second outer circuit layer formed on an outer surface of thesecond insulating layer; wherein the first device and the second deviceare formed in a line in a direction perpendicular to the insulatingmember's plane and in a same cavity, and wherein the thickness of thethird device is thicker than a sum of the thicknesses of the firstdevice and the second device.
 2. The embedded printed circuit board asset forth in claim 1, further comprising: a first via for electricallyconnecting the first outer circuit layer with the first device; a secondvia for electrically connecting the second outer circuit layer with thesecond device; and a third via for electrically connecting the secondouter circuit layer with the third device.
 3. The embedded printedcircuit board as set forth in claim 1, wherein the first base substrateand the second base substrate are formed of a metal layer.
 4. Theembedded printed circuit board as set forth in claim 1, wherein thefirst base substrate comprises a first core layer and a first innercircuit layer formed on an outer surface of the first core layer, andthe second base substrate comprises a second core layer and a secondinner circuit layer formed on an outer surface of the second core layer.